Sarcopenia caused by degeneration of spinal nerve, motor nerve, or skeletal muscle fiber is a representative intractable diseases of which the etiology has not yet been clarified. According to studies conducted thus far, it is known that contraction of skeletal muscles does not occur due to degeneration of motor nerves inducing contraction of skeletal muscles, normal contraction of skeletal muscles does not occur due to reduced expression (sarcopenia) or modification of proteins involved in muscle contraction in the skeletal muscles, and motor nerves or skeletal muscles are modified to fibrous tissues in the long term. As such, since the underlying cause of sarcopenia has not been identified, and methods capable of preventing or restoring degeneration of motor nerves or skeletal muscles have not been developed, studies are presently underway in order to develop a method of slowing the progression of sarcopenia.
As a method of slowing the progression of sarcopenia, a method of inhibiting muscle atrophy caused by degenerative or progressive modification of myocytes, which is a kind of sarcopenia, is mainly used. For example, WO 2007/088123 discloses a therapeutic agent for muscle atrophy including a nitrooxyderivative as an active ingredient, and WO 2006/081997 discloses a therapeutic agent for muscle atrophy including atraric acid or a derivative thereof as an active ingredient. However, since these therapeutic agents including the compounds as the active ingredients act on smooth muscles or cardiac muscles which are not associated with muscle atrophy, as well as on skeletal muscles in which muscle atrophy occurs, a variety of major or minor side effects may be caused, and therefore, the therapeutic agents do not have practical application. Although hormone agents have side effects, their side effects are remarkably reduced as compared with chemical agents, and the hormone agents have bio-friendly properties. Therefore, development of hormone-like agents is being accelerated.
Meanwhile, muscle atrophy is a disease in which muscles of the legs and arms are atrophied, and represented by amyotrophic lateral sclerosis and spinal progressive muscular atrophy, which are known as diseases caused by progressive modification of motor nerve fibers and cells in the spinal cord.
Specifically, spinal muscular atrophy is known as a genetic disorder and neuromuscular disease caused by modification of motor neurons in the spinal cord. Further, amyotrophic lateral sclerosis is characterized by intractable, irreversible neurodegenerative changes due to the death of upper motor neurons and lower motor neurons in the cerebrum and spinal cord, and its main cause is known to be lack of nerve growth factor and neuritis.